Phenolics are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Plant polyphenols have drawn increasing attention due to their potent antioxidant properties and their marked effects in the prevention of various oxidative stress associated diseases such as cancer. In the last few years, the identification and development of phenolic compounds or extracts from different plants has become a major area of health- and medical-related research. This review provides an updated and comprehensive overview on phenolic extraction, purification, analysis and quantification as well as their antioxidant properties. Furthermore, the anticancer effects of phenolics in-vitro and in-vivo animal models are viewed, including recent human intervention studies. Finally, possible mechanisms of action involving antioxidant and pro-oxidant activity as well as interference with cellular functions are discussed.

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Plant phenolics: extraction, analysis and their antioxidant and anticancer properties.

Immune evasion in cancer: Mechanistic basis and therapeutic strategies

This review focuses mainly on eudicot seeds, and on the interactions between abscisic acid (ABA), gibberellins (GA), ethylene, brassinosteroids (BR), auxin and cytokinins in regulating the interconnected molecular processes that control dormancy release and germination. Signal transduction pathways, mediated by environmental and hormonal signals, regulate gene expression in seeds. Seed dormancy release and germination of species with coat dormancy is determined by the balance of forces between the growth potential of the embryo and the constraint exerted by the covering layers, e.g. testa and endosperm. Recent progress in the field of seed biology has been greatly aided by molecular approaches utilizing mutant and transgenic seeds of Arabidopsis thaliana and the Solanaceae model systems, tomato and tobacco, which are altered in hormone biology. ABA is a positive regulator of dormancy induction and most likely also maintenance, while it is a negative regulator of germination. GA releases dormancy, promotes germination and counteracts ABA effects. Ethylene and BR promote seed germination and also counteract ABA effects. We present an integrated view of the molecular genetics, physiology and biochemistry used to unravel how hormones control seed dormancy release and germination.

/pdf/plant-hormone-interactions-during-seed-dormancy-release-and-1j1jryedp5.pdf

Plant hormone interactions during seed dormancy release and germination

Unravelling cadmium toxicity and tolerance in plants: Insight into regulatory mechanisms

This article reviews the responses of plant roots to elevated rhizosphere cadmium (Cd) concentrations. Cadmium enters plants from the soil solution. It traverses the root through symplasmic or apoplasmic pathways before entering the xylem and being translocated to the shoot. Leaf Cd concentrations in excess of 5-10 μg g(-1) dry matter are toxic to most plants, and plants have evolved mechanisms to limit Cd translocation to the shoot. Cadmium movement through the root symplasm is thought to be restricted by the production of phytochelatins and the sequestration of Cd-chelates in vacuoles. Apoplasmic movement of Cd to the xylem can be restricted by the development of the exodermis, endodermis, and other extracellular barriers. Increasing rhizosphere Cd concentrations increase Cd accumulation in the plant, especially in the root. The presence of Cd in the rhizosphere inhibits root elongation and influences root anatomy. Cadmium concentrations are greater in the root apoplasm than in the root symplasm, and tissue Cd concentrations decrease from peripheral to inner root tissues. This article reviews current knowledge of the proteins involved in the transport of Cd across root cell membranes and its detoxification through sequestration in root vacuoles. It describes the development of apoplastic barriers to Cd movement to the xylem and highlights recent experiments indicating that their maturation is accelerated by high Cd concentrations in their immediate locality. It concludes that accelerated maturation of the endodermis in response to local Cd availability is of functional significance in protecting the shoot from excessive Cd loads.

Root responses to cadmium in the rhizosphere: a review

Brassinolide [2α, 3α, 22R,23R-tetrahydroxy-24S-methyl-B-homo-7-oxa-5-α-cholestan-6-one] and its related compounds, brassinosteroids, applied at the early stages of conditioning shortened the conditioning period required before clover broomrape seeds would germinate after exposure to germination stimulants, such as dl-strigol and natural stimulants from red clover (Trifolium pratense L.) root exudate. Brassinosteroids applied after conditioning increased the rate of the seed germination induced by these stimulants. The inhibitory effect of light on seed germination when it was induced by dl-strigol could be overcome by brassinosteroids. Brassinosteroids also eliminated the inhibitory effects of light and dl-strigol applied at the early stages of conditioning. GA3 was also effective in causing seed conditioning and increased the rate of the germination induced by these stimulants. There was a relationship between brassinosteroids and GA3 in many of the experiments conducted. These findings may have practical implications in increasing the effectiveness of applying germination stimulants in the field to soils for ‘suicidal germination’ of broomrape seeds.

Effects of brassinosteroids on conditioning and germination of clover broomrape (Orobanche minor) seeds

The present study was conducted to find useful weed species for cadmium (Cd) phytoremediation. Ninety-three weed species and eight crop species were grown for 2 months in pots containing sandy loam soil with 3 mg Cd kg−1 dry weight (DW). The Cd concentrations in the shoots and roots of all species were determined by inductively coupled plasma optical emission spectroscopy and atomic absorption spectrometry. Shoot Cd concentrations (mg kg−1 DW) of Cichorium intybus (77.0) and Matricaria chamomilla (64.4) were higher than that of Polygonum thunbergii (56.2), which is a recognized hyperaccumulator. Root Cd concentrations (mg kg−1 DW) were relatively high (≥ 100) in 11 species, for example, Oenothera biennis (171.9), Calystegia sepium var. americana (122.6) and Cassia obtusifolia (122.2). Shoot–root ratios (ratio of shoot and root Cd concentrations) were higher in Compositae species, for example, Cichorium intybus (3.56) and Bidens frondosa (3.30), than in Gramineae species, for example, Oenothera bi...

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1747-0765.2008.00288.x

Cadmium accumulation in the shoots and roots of 93 weed species

Several fungal metabolites were examined for their effects on germination of the root parasitic weeds witchweed, Striga hermonthica (Del.) Benth, and clover broomrape, Orobanche minor Smith. Among ...

Cotylenins and Fusicoccins Stimulate Seed Germination of Striga hermonthica (Del.) Benth and Orobanche minor Smith

We conducted a comparative study of 20 antioxidants including antioxidative vitamins and polyphenols to examine their inhibitory activities against the in vitro invasion, growth and experimental lung metastasis of murine colon 26-L5 carcinoma cells. Among the compounds tested, epigallocatechin gallate (EGCG), gallocatechin gallate and genistein exhibited significant reductions at 77%, 46% and 44% in tumor metastasis by an intraperitoneal administration for 5 d beginning at 3 d before tumor inoculation, respectively. Quercetin also showed a slight but not statistically significant inhibition. Alpha-tocopherol, beta-carotene, ascorbic acid and 2 EGCG-related compounds of epicatechin gallate and epigallocatechin had no effect. EGCG also inhibited tumor metastasis dose-dependently with 98% suppression at 2 micromol; and an almost equivalent inhibition was also produced by only pre-administration of EGCG at the same dose before tumor inoculation. EGCG significantly inhibited tumor cell invasion and proliferation, but its inhibition of these activities was much less effective than that of other compounds which did not show any antimetastatic effect. No statistically significant relationship was observed between the radical scavenging activities of the test compounds and their rates of inhibition of tumor metastasis. The antimetastatic mechanism of EGCG thus seems to be independent of its inhibition of tumor invasion and growth, as well as its radical scavenging activity. Our results suggest that EGCG is potentially beneficial for tumor metastasis inhibition.

Differential effects of antioxidants on the in vitro invasion, growth and lung metastasis of murine colon cancer cells.

Laboratory experiments were conducted to examine the allelopathic potentials of rice plants (Oryza sativa L.) on seed germination and radicle elongation of Monochoria vaginalis (Burm. f.) Presl var. plantaginea (Roxb.) Solms-Laubat. To compare the relative allelopathic potentials of rice plants at different growth stages, aqueous extracts of dried tissues were obtained from the seeds, husks, and seedlings harvested 10, 20, 40 and 120 days after seeding. When M. vaginalis seeds were incubated in solutions containing aqueous extracts, significant increases in the germination rate were observed for all the aqueous extracts except for the extract of 10 d-old shoots at higher dosages. When partitioned with ethyl acetate, the germination-promoter(s) in the aqueous extracts remained in the aqueous phase while some inhibitors were extracted with ethyl acetate. In contrast, aqueous shoot extracts added to the incubation media at the same dosage for promotion of seed germination inhibited radicle elongation of M. vaginalis, indicating that the sensitivity of the weed varies between these two growth stages.

Masaru Ogasawara

Papers

Effects of brassinosteroids on conditioning and germination of clover broomrape (Orobanche minor) seeds

Cadmium accumulation in the shoots and roots of 93 weed species

Cotylenins and Fusicoccins Stimulate Seed Germination of Striga hermonthica (Del.) Benth and Orobanche minor Smith

Differential effects of antioxidants on the in vitro invasion, growth and lung metastasis of murine colon cancer cells.

Effects of aqueous extract of rice plants (Oryza sativa L.) on seed germination and radicle elongation of Monochoria vaginalis var. plantaginea